how to create an animation that will not use too much menory — Symbian C++

What is the best way to create a longer (few seconds) animation (and not too memory consuming).
Is it better to have every animation step in a single Bitmap (or reuse whenever possible) or is it better to have animated gifs (or more animated gifs)? Or is there another way?

Is it possible to play to animated gifs after each other and still have a smooth animation (so the user will not see that it contains of seperated animated gifs)?

I want to have the animation transparent on the background. Is it possible to have two animated gifs - one with the animation itself and one with the mask?

Thanks for the answers in advance
PengoX